Central Heating Clean Up?

[bungeejumper]

The plumber fitted the boiler and pump, and the system has been running well for eight years.

Indeed, fair points, but if I understand you correctly, the eight year old pump has just been replaced, and that your problems have since got worse? (Not that eight years was much of a life span for the old pump anyway. )

But I'm inclined to agree with you that air is probably causing your current prob. That will either be hydrogen from the radiators (open question - is it still considered safe to put a match to a bleed valve? ), or a leak into the pump (not very likely, TBH), or fresh air that's somehow entering the system, which would mean that it's being actively sucked in. If the latter, t'would be better to find out where and why. Not to say, a lot cheaper.....

BJ

[GeoffF100]

It is not worse. The system did not work at all. The pump was bled. The system still did not work well. The pump was replaced. The plumber said that was speculative. It would either fix the problem or tell us that the problem was something else. The system did not seem too bad until he left. The next step is to try to expel any air from the system, which might fix the problem. The plumber says that air can get into the system via the feed pipe with vented systems. The sure fire cure is a pressurised system. Here are the pros and cons:

https://london-plumber.co.uk/faq/heatin ... or-vented/

[supremetwo]

It is not worse. The system did not work at all. The pump was bled. The system still did not work well. The pump was replaced. The plumber said that was speculative. It would either fix the problem or tell us that the problem was something else. The system did not seem too bad until he left. The next step is to try to expel any air from the system, which might fix the problem. The plumber says that air can get into the system via the feed pipe with vented systems. The sure fire cure is a pressurised system. Here are the pros and cons:

https://london-plumber.co.uk/faq/heatin ... or-vented/

I have this very good Honeywell automatic air vent at the highest point on my vented system:-
https://www.grahamplumbersmerchant.co.u ... d-18-x-38/

[88V8]

The plumber says that air can get into the system via the feed pipe with vented systems.

The feed is underwater. How can air get it. Unless the ball valve fails and header tank dries out, the only way air gets in is if the system is 'pumping over' which happens when water routinely and erroneously flows up the vent pipe and aerates as it falls back into the header tank. This may be caused by bad pipework design or, as has been said, pipe blockage.

Air in the system is rarely air. Usually it is marsh gas produced by corrosion due to lack of inhibitor.
When you bleed the rads, does the 'air' smell pongy?

Ivor

[GeoffF100]

The plumber says that air can get into the system via the feed pipe with vented systems.

The feed is underwater. How can air get it. Unless the ball valve fails and header tank dries out, the only way air gets in is if the system is 'pumping over' which happens when water routinely and erroneously flows up the vent pipe and aerates as it falls back into the header tank. This may be caused by bad pipework design or, as has been said, pipe blockage.

Air in the system is rarely air. Usually it is marsh gas produced by corrosion due to lack of inhibitor.
When you bleed the rads, does the 'air' smell pongy?

Ivor

More accurately, the plumber said that a blockage in the fed pipe can prevent water getting in to the system. Less water = more "air". The radiators have all been bled. When radiators are bled, a lighted match shows that there is flammable gas, but that is normal.

[88V8]

More accurately, the plumber said that a blockage in the fed pipe can prevent water getting in to the system. Less water = more "air". The radiators have all been bled. When radiators are bled, a lighted match shows that there is flammable gas, but that is normal.

There should never be a blockage. The header tank should have a well-fitting lid, as part of its insulation.

Marsh gas is a corrosion product.
Your rads are rusting. Perhaps due to air, if the pipe has blocked, more likely due to lack of inhibitor. The black sludge is sometimes called magnetite, another corrosion product. Dissolved steel. It used to be part of the your radiators, which are now on the way to pinholing due to rust.

Inhibitor can become diluted to the point of ineffectiveness. Perhaps by leaks, or partial draining without new inhibitor being added.

To prevent this one needs to check the header tank at least annually, and ensure there is sufficient inhibitor. In the same way that one checks the antifreeze/corrosion inhibitor in one's car.
Here is an example of a checker for the concentration.
https://www.sentinelprotects.com/uk/pro ... k-test-kit

The heating system that I designed and installed in our previous house gave no trouble in 29 years, other than a couple of valve motors. The gas boiler was never serviced nor did it need to be. The rads never needed routine bleeding, and when I had to bleed them after decorating, there was no gassy pong. The feed pipe did not block. The pump was the original. The (cast iron) rads did not clog up, there was no black in them.

All that was necessary to maintain this nirvana was an annual peek at the header tank, and a check on the inhibitor.

And the same will work for you.

Ivor

[bungeejumper]

The plumber says that air can get into the system via the feed pipe with vented systems.

The feed is underwater. How can air get it. Unless the ball valve fails and header tank dries out, the only way air gets in is if the system is 'pumping over' which happens when water routinely and erroneously flows up the vent pipe and aerates as it falls back into the header tank. This may be caused by bad pipework design or, as has been said, pipe blockage.

What 88V8 said. I don't really want to get back into this, but I'd just add two quick points about "pumping over", which was what I rather clumsily described in my first response. Might be worth a look?

The first is that if your header tank is pumping over, its contents will be noticeably warm or even hot. This really shouldn't be happening! At the extreme end of the problem, there have been some horrible accidents where header tanks have actually dumped their scalding contents through the ceiling onto some poor sod's bed. Not a nice way to go.

The second is that there's a really simple test for a blocked 28mm pipe causing feedback into the header tank. Get yourself a small powerful magnet ("supermagnet"), and check the 28mm copper pipe just upstream/downstream of the feed pipe. If the magnet sticks, you've got iron deposits in there. Mine did! Diagnosis complete.

Take a look. Will take you moments, and what have you got to lose?

BJ

[GeoffF100]

The plumber did those checks and decided that was not the problem. Hopefully, he will be returning next week. The next step is to try to blow air out of the system with mains water pressure.

[bungeejumper]

More accurately, the plumber said that a blockage in the fed pipe can prevent water getting in to the system. Less water = more "air". The radiators have all been bled. When radiators are bled, a lighted match shows that there is flammable gas, but that is normal.

You are being told two incompatible things. If the gas in your radiators is flammable, then it didn't get there through your header tank. If air had been sucked in in that way(which is highly improbable), it would have been non-flammable air, not hydrogen.

It's possible, I suppose, that air in the system could have caused the rust that produced your current hydrogen in your radiators - but not in the short time that has elapsed since you last had your system drained down to replace the pump.

It strikes me that your plumber is trying to cure the symptoms, not the cause. If he didn't bleed the system sufficiently after the last drain-down (and yeah, it happens, we're all human ), then turning your system into a sealed circuit now wouldn't correct the situation either. So why is he suggesting it to you? Strongly suggest that you get a second opinion.

BJ

[GeoffF100]

More accurately, the plumber said that a blockage in the fed pipe can prevent water getting in to the system. Less water = more "air". The radiators have all been bled. When radiators are bled, a lighted match shows that there is flammable gas, but that is normal.

You are being told two incompatible things. If the gas in your radiators is flammable, then it didn't get there through your header tank. If air had been sucked in in that way(which is highly improbable), it would have been non-flammable air, not hydrogen.

It's possible, I suppose, that air in the system could have caused the rust that produced your current hydrogen in your radiators - but not in the short time that has elapsed since you last had your system drained down to replace the pump.

It strikes me that your plumber is trying to cure the symptoms, not the cause. If he didn't bleed the system sufficiently after the last drain-down (and yeah, it happens, we're all human ), then turning your system into a sealed circuit now wouldn't correct the situation either. So why is he suggesting it to you? Strongly suggest that you get a second opinion.

BJ

The chronology is wrong here. Many years ago another plumber got methane out when he bled a radiator. There was corrosion then. There is no gas in any of the radiators now. The current plumber was not the last plumber to drain down the system. (He thinks he was, but that is different matter. I should have told him. The system was drained down by another plumber about five years ago to fit new radiator valves.)

The plumber did not think that air got through from the header tank. He checked for a blockage in the feed pipe, but did not find one. Converting the system into a pressured system should stop the feed pipe getting blocked, and he suggested that it might be a good idea. The header tank is full of brown sludge, so something has to be done there. The plumber thought the problem was air in the pump and bled it, which silenced the system for about an hour. He then suspected a faulty pump. Changing the pump silenced the system for about an hour.

The system runs noisily for a few days heating most of the radiators. It then becomes quieter, and the downstairs radiators go cold. If I turn the system off for an hour, it becomes noisy again and heats most of the radiators. No further diagnosis has yet been made, and no solution has been proposed. He is going to try blowing air out of the system with mains water pressure.

[Plumberian]

More accurately, the plumber said that a blockage in the fed pipe can prevent water getting in to the system. Less water = more "air". The radiators have all been bled. When radiators are bled, a lighted match shows that there is flammable gas, but that is normal.

You are being told two incompatible things. If the gas in your radiators is flammable, then it didn't get there through your header tank. If air had been sucked in in that way(which is highly improbable), it would have been non-flammable air, not hydrogen.

It's possible, I suppose, that air in the system could have caused the rust that produced your current hydrogen in your radiators - but not in the short time that has elapsed since you last had your system drained down to replace the pump.

It strikes me that your plumber is trying to cure the symptoms, not the cause. If he didn't bleed the system sufficiently after the last drain-down (and yeah, it happens, we're all human ), then turning your system into a sealed circuit now wouldn't correct the situation either. So why is he suggesting it to you? Strongly suggest that you get a second opinion.

BJ

Couldn't agree more. I used to run a plumbing and heating company that specialised in power flushing. Went all over the south and west of England fixing problems that other plumbers could not. Changing to a pressurised system is not going to remove the problem.

Are you able to post a few pics of the pipework in your airing cupboard (or wherever it is that your feed and expansion pipework from/to the header tank is connected)?

Moderator Message:
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[sg31]

Couldn't agree more. I used to run a plumbing and heating company that specialised in power flushing. Went all over the south and west of England fixing problems that other plumbers could not. Changing to a pressurised system is not going to remove the problem.

Are you able to post a few pics of the pipework in your airing cupboard (or wherever it is that your feed and expansion pipework from/to the header tank is connected)?

]

Welcome to Lemon Fool. That's very helpful.

[GeoffF100]

Thank you very much for that, but the game has moved on. (Hopefully, I made it clear that a closed system was suggested as a possibility, if air was entering the system from outside, but that was before before a definite diagnosis had been made.)

The current situation is that my system is noisy. At its best, most of the radiators upstairs are hot, but one of them is only hot at the top. Two small radiators downstairs are hot, but the two big ones are cold, or just a little warm at the top.

After the system has been running for a day or so, the system becomes quieter, but all the downstairs radiators become stone cold. Following the plumber's suggestion, I turn the system off for half an hour and turn it back on again, to let air/gas out of the system. (I think I have heard air/gas gurgling up.) The system then becomes very noisy again, and the two downstairs radiators heat up and the two downstairs big radiators become a little warm at the top.

When I phoned the plumber he suggested that I get a power flush. He does not have the equipment to do that, but said he would recommend someone who does. He has not done that.

It is usually about 15 degrees C downstairs and 17 to 19 degrees C upstairs. I mostly live upstairs and can cope with that. Hopefully, it will be easier to get the problem fixed when the weather gets warmer and the plumbers have less business.

I expect that my problem is corrosion and sludge building up in the radiators. A closed system will not fix that. Is a power flush the best way forward? If so how do I go about finding someone who will do a good job at a reasonable price?

[GeoffF100]

Irrelevant now, but I am not quoting accurately what I was told about closed systems. I think the benefit was that crud could not enter the system and block up the feed pipe. The plumber did not think that was happening though, because water was coming through to the pump, when he checked for that.

Having said that, the feed tank is full of brown sludge, so that has to fixed too.